A veteran detective says the parents of a missing Indiana University student should not give up hope.

Charlene and Robert Spierer are preparing to mark the six month anniversary of the day their daughter Lauren disappeared.

Arm in arm, outside their daughter's apartment complex Friday, Robert and Charlene Spierer made an emotional plea. It's one they've shared over and over for six agonizing months.

"What do you need from us? What can we do to convince you to give us our daughter back? I beg you to give us Lauren," Charlene Spierer said.

The posters and public searches, the police and now a private eye are all still seeking Lauren Spierer.

The 20-year-old IU student disappeared after a night out with friends in June. Each month since has marked a painful milestone for her parents.

They've had no answers, even though investigators have combed through more than 2,400 tips.

"We're clinging to the hope that she could be alive. Obviously we want to find her," Robert Spierer said. "The longer that time goes by, obviously, the more frustrated we become with the lack of closure in terms of finding Lauren."

Retired Indianapolis Police detective Robert Snow worked missing persons cases and now writes about them. He says time can be tough. Tips aren't as solid and at some point, the case often stalls.

"Therein lies the problem of course, there's no resolution," Snow said. "Police won't give up, but you simply can't keep expending resources on a case when there's no outcome."

In a statement this week, Bloomington Police said they're still strongly committed to the Spierer case.

Snow says Bo Dietl, the private investigator hired by the Spierers, should help drum up leads as well.

He also says the ending doesn't have to be tragic.

"I have a case in my upcoming book, very similar to the Spierer case. A young lady who disappeared from the University of Texas and was gone for seven years and her mother was having her declared dead and she showed up then, working in a Sam's Club south of Louisville. It's not impossible that the person's still there. The key for the loved ones is never give up hope because people have shown up years and years later."

The Spierers are not giving up. They're now hoping for closure.

"The answer to my prayers would be to find Lauren alive and that we could take her home and help her move on from this horrible time in her life. At the very least, we want to find Lauren and that's what we are desperately hoping for, is to find Lauren and take her home," Charlene Spierer said.

A vigil will be held Saturday night in Bloomington. People will gather at the Smallwood Apartment complex, where Lauren lived, then walk to the Monroe County Courthouse where people can attach messages of support to a tree for Lauren's family.

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A vigil will be held Saturday night to mark six months since the disappearance of Indiana University student Lauren Spierer.

Spierer disappeared early in the morning of June 3 after a night out with friends near the IU campus. Bloomington Police say they've received more than 2,400 tips in the case.

"We know that they're working on a number of leads over the past few months. We continue to get tips to come in either to the FindLauren.com web site or through the PO Box. Occasionally we get direct calls, but there have been a number of different sources that have provided information, which we turn over to the police," said Lauren's father, Robert, in an interview Friday with Eyewitness News.

"The longer that time goes by, obviously, the more frustrated we become with the lack of closure in terms of finding Lauren. As parents, we find it inconceivable how people could go about their lives, those who know what happened to Lauren, without coming forward and bringing relief to us as a family or to IU or the Bloomington community. This is a shared experience here and it's been a terrible one for six months now," he continued.

Some of the tips include the names of individuals who should be considered as possibly involved in her disappearance. But so far, none of those tips have led to a major break.

"We're also reaching out to someone who knows about Lauren's disappearance, knows where she is, but has yet to come forward, for whatever fear or apprehension you have, we ask you to please come forward anonymously," Spierer said. "There's so many ways to get to us, find our daughter and to get closure with this terrible episode in our lives."

"I beg you, again, for the numerous time, to give us the information that we need to lead us to Lauren. And I would also ask the question, 'What do you need from us? What can we do to convince you to give us our daughter back?' I beg you to give us Lauren," said Lauren's mother, Charlene.

Robert Spierer says he and his wife are "clinging to the hope" that their daughter could be alive, that she's technically still classified as a missing person.

"Obviously, we want to find her. "It's been six months now and a lot of effort has gone into trying to find Lauren. Unfortunately, the person or persons that know where she is or what happened to her are refusing to come forward and give us that information," he said.

"I have to only hope that we find Lauren and the answer to my prayers would be to find Lauren alive and that we could take her home and help her move on from this horrible time in her life. At the very least, we want to find Lauren and that's what we are desperately hoping for, is to find Lauren and take her home," Charlene Spierer said.

Saturday's vigil will be held at 7 p.m. outside the Smallwood Plaza apartments where Spierer lived.